This invention relates generally to lubrication of components, and more specifically to lubrication of a bearing coupled to a blade.
At least some known wind turbines have a bearing coupled between a blade and a hub with a pitch motor positioning the blade attached to the bearing. When the blade remains in the same position for an extended period of time, the bearing required torque will increase as the lubricant in worked out of the bearing raceway through the micro-movements. The more torque the mechanism draws to pitch the blade, the more heat the mechanism generates. In some cases, the heat can delaminate the windings of the mechanism causing mechanism failure. Due to increased friction in the bearing, the bearing could wear and not reach its designed lifetime. In some wind turbines, the blades are up to 60 meters in length, but may be designed to be up to 100 meters, so removal to change a worn bearing can be costly and time consuming. Other known wind turbines are offshore, requiring extensive equipment to remove a blade and replace the bearing. Wind turbines hub heights can be over 120 meters and in high winds, making it dangerous for workers to be on the wind turbines.
A worn bearing can also cause a blade to move out of a pitch setting such that the blades of the wind turbine asymmetrically load the hub and rotor shaft. If the rotor begins to move within the stator due to the asymmetric loading, there is a possibility of the rotor contacting the stator, for example, in direct drive application with the turbine rotor being attached directly to the generator. An electrical transient can occur if the rotor and stator contact, and the wind turbine may then have to be taken off-line.